10 - Effect of different concrete materials on the corrosion of the embedded reinforcing steel

Abstract

Repair and rehabilitation of concrete structures in the United States have been estimated at $20 billion annually; approximately 40% of that cost is due to corrosion of embedded steel reinforcement, with much of the corrosion damage occurring in bridges. In the United States, about $4 billion is spent annually to maintain and replace corroded bridge structures. Chloride ingress and carbonation at the internal reinforcing steel level are two major factors contributing to reinforcement corrosion. This chapter reviews the influence of the water-to-cementitious-materials (w/cm) ratio, curing methods, supplementary cementitious materials (SCMs), alternative binders, and other admixtures on the corrosion of embedded steel reinforcement in concrete structures. Each of these parameters affects the ingress of chlorides as well as the natural carbonation of the concrete. The influence of the concrete mixture is shown to have significant effects on the resistance to corrosion of embedded reinforcing steel. Creating a concrete mixture with a dense, impermeable microstructure such as a low w/cm mix design containing SCMs and providing curing conditions to increase maturity prior to exposure will maximize corrosion resistance. There is no single mix design that will result in the best performance for all applications; however, the particular application should be considered to develop a concrete mix design that will provide the necessary durability for a project. Advances in cementitious and reinforcing materials and mixture design offer new approaches for mitigating corrosion in aggressive environments.